Second part of precision farming

• Crop sensing by reflectance– Greenseeker

• Measuring fluorescence and photosynthesis– Yara N-tester

• Using Vegetation index – NDVI or WDVI or NDRE (Reliable yes or no)

• Basics of crop Sensing– Remote or near sensing or taking pictures !!

VI

Height above crop

Wavelenght of light

• Red 650-780• Orange 585-650• Yellow 575-585• Green 490-575• Blue 420-490• Violet 380-420• UV < 380• NIR > 780

colourspectrum

Light response

Absorption by plastiden

Chlorofyl

Questions

• Why looks a leaf of a crop green or purple(red)• What do measure when you use sensors:1. Reflection of light of an certain wavelength2. Fotosynthesis activity 3. Both 1 + 2• When the UAV is being used how is this sensor

working.1 to 3 or just making pictures (RGB-red/green/blue)

What do we see and pigment abs

Photosystem…fluorescentie

What can be done by sensing

• Crop sensing (NIR)– Irrigation (soil sensor or Water watch; energy)– Nutrition– Crop protection

• Biomass sensing (UV)• Soil sensing (Gamma Ỵ-radiation)

Precision circle

potato planting

Plantdensity

• When you want to harvest potatoes for consuming (eating) or processing (chips)

• In case of cultivation of seed potato variable planting (4 % more yield by change density 10 %)

• What is the best density– Smaller than 75 cm– Closer than 30 cm

• How do you translate density of a potatocrop– Seedpotato/m2 or stems/m2

Normal

Density between wheels

• In case of seedpotato variation in density seems to have some effect.

Close planting

• In a situation when lutum is changing usefull• 10 % more plants where lutum is 10 % lower

Plantdensity in the shade

• Zones: I = 40 %; II = 60 % en III = 80 en IV = 100• Shade less dense ??

Shade or Far red

Reaction in stem elongation

Shade versus light

• How important is light for crop growth• Fotosynthese depends of light• LAD and yield is lineair• Lack of water and/or light causes shortage of

tubers and that is why the influence of light is less important. Especially when tuber set takes place the need of water is high.

Digistaat

• Injection of highly concentrated (pig) manure with N and K (no P !!) and looks like KAS

• Better is injection because otherwise you get NH3 into the air.

Side dress N rate in potato

• Crop reflectance to determine sidedress N !• WDVI is related to N-uptake (calibration)• Instead of collecting petioles (Nitrate, BSO)• Neither taking soil samples (ALTIC)• BUT: Reflectance may be caused by other

factor than N, such as: Drought, water logging, disease, genotype, insect damage, nematode, soil structure, other nutrients and weeds !!

Side dress P, K in potato ?

• Crop sensing for P shortage can be done• Potasium as no relationship with sensing and it

seems that N/K-ratios can be measured.• Modelling with photosynthesis-light-curve if hyper -

or ultraspectral bands are being used.

Nutrient deficiencies

Sucros

Measuring is knowing

• What do you decide– Improve bad spots– Speeding up yield (SUSY) on good spots

• When side dressing for N is only 30 – 50 kg– Is this usefull when sensing gives this advice?

• When you know that the NBI for the efficiency of nitrogen is not more than 50 %; what is the use of sensing…